Maybe it would help to say that "save to disc" in Calibre just means "save to your designated drive"? It can be your hard drive, a flash drive, a removable drive...
It really isn't designed for creating CDs or DVDs - even though most of us are probably more used to thinking of those as discs than our various drives.
I didn't understand your question at first because I've been using Calibre for so long that I didn't associate "save to disc" to burning a CD or DVD.
HTH
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